Preheat the oven to 180°C (th.6).
Peel, core and cut the apples into thin strips.
In a bowl, mix the apples with the brown sugar, vanilla sugar and cinnamon. Let stand for 10 minutes so that they soak up the flavours.
Unroll puff pastry on a baking sheet covered with baking paper. Prick the bottom lightly with a fork.
Spread the apples over the dough, leaving a 2cm free edge all around.
Brush the edges with a little water, then cover with the second puff pastry. Seal the edges by pressing down with fingers or a fork.
Make a few cuts on the top to let the steam escape.
Brush with egg yolk mixed with a little milk for a nice egg wash.
Bake for 30 to 35 minutes, until the crisp is golden brown and crispy.
Let cool before sprinkling with icing sugar and enjoy!
A crispy and melting dessert, perfect to accompany a coffee or a scoop of vanilla ice cream!